Piezoelectric elements are widely used in a variety of electronic components including ceramic resonators, ceramic filters, piezoelectric displacement elements, buzzers, transducers, ultrasonic receivers and ultrasonic generators, etc. As a result of the increased demand for piezoelectric elements, there is an increasing use of piezoelectric ceramic compositions to form the elements. The different uses or applications require different electromechanical characteristics from the piezoelectric ceramics. Additionally, there is a continued drive towards increasingly smaller electronic components, causing an increased demand for smaller piezoelectric elements for use in these electronic components. However, many of the smaller electronic components require that the piezoelectric elements provide the same or even greater output power, despite their reduced size.
Existing high power piezoelectric ceramics often do not exhibit suitable electromechanical properties for use in miniaturized electronic devices, such as miniaturized ultrasonic devices. In the current state of the art, the existing piezoelectric elements that are sufficiently small to be used in the miniaturized devices exhibit low capacitance and high electrical impedance. This is inadequate to drive the miniaturized devices. Additionally, if the permittivity is high, the dielectric loss factor (tan δ) of the current piezoelectric elements is also high—resulting in internal heating and dissipative loss which significantly decreases the efficiency and output of the device. Consequently, existing piezoelectric ceramics have not provided adequate electromechanical properties for these miniaturized electronic devices.
The electromechanical properties of the piezoelectric ceramics can be altered by varying the specific ceramic composition, the molecular structure, and/or the methods and parameters for fabricating the piezoelectric ceramic.
Common piezoelectric ceramics can be formed from of a variety of general classes or types of ceramics. One class is a lead-zirconium titanate ceramic (PZT); another class is a lead-magnesium niobium ceramic (PMN). In many cases, solid solutions of either the PZT or the PMN ceramic are prepared in which dopants are distributed either homogeneously or inhomogeneously in the general PZT or PMN ceramic. The dopants can be found in the interstitial spaces of the crystal units of the bulk matrix. They can modify characteristics to the resulting piezoelectric ceramic, including the Curie temperature, the mechanical quality factor, the dielectric dissipation factor, and the dielectric strain constant, among others.
In light of the above problems, there is a continuing need for advances in the relevant field including new piezoelectric ceramic compositions and piezoelectric elements formed from the compositions. The present invention addresses that need and provides a wide variety of benefits and advantages.